Precast staircase

ABSTRACT

A precast reinforced concrete integral staircase adapted to be installed as a unit to span the space between two landings is formed of a deep U-shaped elongated beam member wherein the arm portions of the U extend upwardly from the flat base of the U defining the stairs to provide a supporting structure for the stairs, which arms also become a rail for safety purposes during construction and as a permanent rail thereafter.

United States Patent 1191 Hanson Apr. 23, 1974 1 PRECAST STAIRCASE [75]Inventor: David W. Hanson, Minneapolis,

Minn.

[73] Assignee: Fabcon, lnc., Savage, Minn.

[22] Filed: Sept. 25, I972 [21] Appl. No.: 291,697

[52] U.S. Cl. 52/190, 52/723 [51] Int. Cl. E041 11/14 [58] Field ofSearch 52/189, 190, 191, 184-186,

[56] References Cited UNITED STATES PATENTS 3,720,024 3/1975 Theisen52/185 1,291,904 1/1919 Itschner..... 52/182 2,721,472 10/1955 McAver52/191 3,307,308 3/1967 Lyons 52/190 FOREIGN PATENTS OR APPLICATIONS26,666 10/1953 Finland 52/182 1,166,294 4/1958 France.... 52/7231,121,200 7/1956 France 52/185 10/1960 Austria 52/189 1,080,235 12/1954France..... 52/182 1,082,834 1/1955 France 52/182 1,150,513 1/1958France 52/182 1,161,495 9/1958 France 52/191 1,252,811 12/1960 France52/184 172,886 9/1960 Sweden 52/182 Primary Examiner-Henry C. SutherlandAssistant Examinerl-Ienry E. Ruduazo Attorney, Agent, or Firm-Schroeder,Siegfried, Ryan & Vidas [5 7] ABSTRACT A precast reinforced concreteintegral staircase adapted to be installed as a unit to span the spacebetween two landings is formed of a deep, U-shaped elongated beam memberwherein the arm portions of the U extend upwardly from the flat base ofthe U defining the stairs to provide a supportingstructure for thestairs, which arms also become a rail for safety purposes duringconstruction and as a permanent rail thereafter.

5 Claims, '7 Drawing Figures 1 PRECAST STAIRCASE The present inventionis in the fluid of preformed structural members for buildings and thelike wherein component units of a building are formed at a site remotefrom the actual building site, transported to the building site as aunit and then installed to form the building. More specifically, thepresent invention is directed to a precast staircase member formed ofreinforced concrete adapted to be installed as an integral unit betweentwo landings.

The use of precast panels of concrete to form the floor and ceiling iswell known in the art and has found considerable usage in recent yearswhere apartment buildings and the like are to be erected in a relativelyshort period of time. Precast concrete stairs for such construction havenot heretofore been available which include the desirable features ofgreat structural strength, relatively low weight for easier handling andinstallation and which meet the requirements of the Occupational Healthand Safety Act. The Act among other requirements makes it mandatory thatwhere building construction is being undertaken all stairways must beenclosed by a railing to protect the workmen from injury due to fallsoff the side thereof during the construction period for the building. I

In accordance with the present invention there is provided a staircasewhich possesses the necessary strength, isof relatively light weightandhas an integral part of its structure railing members meeting the safetyrequirements. Briefly, the staircase of the present invention involves adeep U-shaped elongated beam member wherein the vertical portions of thebeam form rails and further provide theprincipal sourceof support of thestairs which are suspended from the rail portions. The invention will beunderstood from a study of the following specification and 'drawings.

- "IN THE DRAWINGS FIG. 1 is a perspective view of a staircase inaccordance with the invention shown spanning an'opening between twolandings; FIG. 2 is an elevational view incross section of the FIG. '3is across-sectional view along lines 3-3 of FIGS. 1 and 2;

FIG. 4 is an elevational view in cross section of a mold used informingthe 'staircaseof FIG. 1;

FIG. 5 is a sectional view of the 'mold ofFIG. 4 along lines 5-5;

FIG. 6 is a side'elevational viewof aportion of the reinforcingsteelc'ageat theupp'erpart of the staircase;

and

FIG. 7 is a perspective view of a supportin'gplate'and reinforcing rodsof 'FIG. 6.

In eachof the several views like parts will' be given the samenumericaldesigriation.

Inthe drawings 10 generally designates a staircasein accordance with thepresent invention. The staircase comprises a broad flatbottomed*U-shaped beam wherein the arms of the'U'are designated 1 1 and 12respectively. The lower flatportion of theU- intermediate the armsformsthe stairs 15. The upper portion of staircase 10 rests upon alanding or upper floor 13 while the lower portionof the staircaseissupported "bylanding l4. Rails 11 and 12 have a relieved portion 16 and17 respectively which is shaped to engage'floor 13. The lowerportion ofthe staircase and rails ll-and 12 has a flat beveled portion 18 adaptedto rest upon floor 14. The entire staircase is formed in such a manneras to be a one-piece cast reinforced concrete member.

Referring to FIG. 2 there is illustrated in crosssectional view thestaircase in accordance with FIG. I. As can be seen staircase railmember 11 (and its corresponding rail 12) are of a parallelogramconfiguration wherein the upper surface of the rails is parallel to thegeneral axis of the stairs and forms the handrail portion thereof. Theupper end of rail 1 1 extends outwardly beyond the top stair 15' withthe outermost edge 19 being angled with respect to the stair so as to beperpendicular to floor 13. The lower edge 20 of rail 11 is similarlyperpendicular to bottom stair 15".

The flat base of the U-shaped beam comprises the stairs 15. The lowerside 29 is cast so as to present a flat smooth surface while the upperside has been shaped to form the stairs 15. In the construction of thestaircase reinforcing rods of steel are utilized. A partial showing ismade in phantom in FIG. 2 of the U-shaped reinforcing rods 21 which arejoined as by welding to stringer rods 22. Both rods 21 and stringers 22extend the length of the staircase to define the cage. Welding of therodsto form the cage extending the length of staircase 10 isaccomplished prior to insertion of the rods into the mold, illustratedin FIGS. 4 and 5, to give additional strength to the overallconstruction.

As the staircase is a mobile unit adapted to be lifted into place by acrane there is provided anchor nuts 23 which may, if desired, be weldedto the cage member formed of the reinforcing rods. These anchor nuts aremoved and the openings in the anchor nuts filled with a suitablematerial so as to present a smooth surface in the finished product.

The readers attention is now drawn to FIGS. 6 and 7 which show detailsof the reinforcing rod construction for the upper portion of thereinforcing cage of the staircase. L-shaped reinforcing rod 24 is weldedto an angleiron 25 which also has joined thereto rod irons 26 whichproject inwardlyinto the concrete which will be poured about theconstruction. Dotted outline 27 .of FIG. 6 illustrates the final outerform of the poured concrete. The function of angle iron 25 is to serveas a support and tie member for the upper portion of staircase 10 in itsjoining to floor 13. The dimensions of angle iron 25 are approximatelythe same as the width of rails 11 and 12 and are positioned directlytherebeneath. The angle iron 25 thus provides a broad support structurefor therail members which in turn act as the support for the stairs l5and adjacent concrete. In actualinstallation a plate of steel 28 is castinto floor slab "13 when it is formed and when staircase 10 is installedplate'25 is joined as by welding to plate 28, thus insuring thatthestaircase does not slip out of position. The lower portion-of staircase10 is not fixedly joined'to floor 14 but merely rests on flat surface 18to permit movement due to expansion and contraction arising fromchanges'in temperature.

As illustrative of dimensions involved in the construction of astaircase in accordance with the invention the following values may betaken as typical. The

staircase for complete spanning of an interfloor distance of 9 feet hasan overall length at the tread portion of about lo hfeet. The overallheight of the rail sections 11 and 12 is approximately 3 feet while theoverall width of the staircase is approximately 4 feet. The thickness ofrail sections 11 and 12 is approximately 3 inches. The minimum thicknessof concrete in the staircase between the back side 29 and bottom ofrisers to stairs 15 is 3 inches. For a staircase with these dimensionsthe weight would be approximately 2 tons.

Construction of a reinforced concrete stair without the use of theU-shaped construction of the present invention would require as aminimum thickness at least 7 inches of concrete between the base of therisers to stairs l5 and the back side of the stair. This heavy thicknessof concrete, absent the deep U-shape construction of the presentinvention, is necessary in order to make the stair self-supporting ofits own weight and the loads to be anticipated in service. Through theuse of the deep U-shaped construction of my invention the stairs aresupported, not by their own strength alone, but are largely supported byhanging from the side rails 11 and 12 which form a high strengthstructural member for such support. As has already been noted angleplates are the supporting surfaces for rails 11 and 12. Very little ofthe support for the stairs portion results from the concrete along thelength of the stair. Rather, individual stairs are principally supportedfrom arms 11 and 12. The overall construction provides not only anextremely strong construction but simultaneously provides an integralrailing with the construction which is immediately serviceable as asafety factor during the construction period aswell as lending itself toa finished staircase appearance after the building has been completed.

Referring now to FIGS. 4 and 5 there is illustrated respectively in sideelevational view and in cross sectional view along lines 55 of FIG. 4 amold for use in forming the staircase of the invention. The mold isconstructed of steel panel members which are joined together as bywelding to form a finished mold used in the inverted staircaseorientation as seen best in FIG. 5. The interior facing surfaces of themold are smooth and are treated with a suitable release agent tominimize any tendency of the fresh concrete to bond thereto. The armportions of the mold 31 and 32 are shaped so that the upper ends ofrails 11 and 12 will be somewhat thinner than the lower portion of therails as an aid to releasing the rail portions from the mold. The treadportions of the mold are formed by angled sheets of steel which arewelded to the side rail forming portions of the mold.

The cradle of reinforcing steel rods, shown in the other views to thedrawings, is introduced into the mold chamber and concrete is pouredtherein to surround the reinforcing rods. The open side of the mold isthen smoothed off to form the smooth back surface of the staircase.After the concrete has become suitably set the mold is freed from thenow formed staircase.

I claim:

1. A mobile unitary precast reinforced concrete staircase and handrailof relatively low weight adapted to span a space between horizontallyand vertically spaced landings comprising a plurality of U-shapedreinforcing rods spaced in generally parallel relationship to oneanother with the arms and base portions of each of said U-shaped rodsbeing in a plane with the corresponding arms and base portions of thebalance of said U-shaped rods longitudinal reinforcing rods extendinggenerally transverse to said U-shaped rods said longitudinal rods beingin spaced and generally parallel relationship to one another with aplurality of longitudinal rods on each arm and on the base portion ofsaid U- shaped rods and welded to said U-shaped rods joining them toform a cage, concrete encapsulating said cage to form a U-shaped beammember with the concrete of the base of said U-shaped beam memberforming a plane on the lower side thereof and being configured on theupper interior facing side thereof into a plurality of riser and treadsurfaces thereby defining a stairs, each of the arm portions of saidU-shaped beam extending upwardly from said stairs being relatively thinin thickness and integral with said base portion and having the overallshape of a parallelogram with the longitudinal sides thereof parallel tothe general plane of the stairs, said arm portions having a height abovesaid tread surfaces corresponding to a hand rail height, thelongitudinally remote ends of said arm portions extending at least toeach end of said stairs and having an angle therewith so as to besubstantially perpendicular to the ground when said staircase isinstalled.

2. In combination first and second horizontally and vertically spacedlandings, the upper of said landings including a steel plate fastenedthereto adjacent the landing edge thereof, a unitary precast reinforcedconcrete staircase of relatively low weight spanning the space betweensaid landings, said staircase comprised of a unitary elongated U-shapedbeam member of reinforced. concrete, the base portion of said U-shapedbeam being configures on the upper interior facing side thereof into aplurality of risers and tread surfaces thereby defining a stairs, eachof the arm portions of said U-shaped beam being relatively thin inthickness and integral with said base portion and having an overallshape of a parallelogram with the longitudinal sides thereof parallel tothe general plane of the stairs, said arms having a height generallycorresponding to a hand rail height, the longitudinally remote ends ofsaid arms extending at least to each end of said stairs with the upperends of said anns extending beyond said stairs, the ends of said armshaving an angle with said stairs so as to be substantially perpendicularto the ground when said staircase is in the installed position, theportion of said arms extending beyond the upper end of said stairshaving a relieved portion at the lower extended edge thereof constructedand arranged to engage an upper surface of the landing, the relievedportion including an angle iron covering the bearing surfaces of saidrelieved portion, said angle iron being joined to reinforcing rodsembedded in the concrete of said staircase, said angle iron also beingjoined to said steel plate on said upper landing to prevent movementthereof with respect to said landing and the lower portion of saidstaircase being in sliding engagement with the upper surface of thelower landing.

3. A mobile unitary precast reinforced concrete staircase and handrailof relatively low weight adapted to span a space between horizontallyand vertically spaced landings comprising: an elongated U-shaped beammember comprised of a unitary body of reinforced concrete; the baseportion of the said U-shaped beam having a plane surface on the outerside thereof and being configured on the upper interior facing sidethereof into a plurality of risers and tread surfaces thereby defining astairs; each of the arm portions of said U-shaped beam being relativelythin in thickness and integral with said base portion and having theoverall shape of a parallelogram with the longitudinal sides thereofparallel to the general plane of the stairs, said arms having a heightgenerally corresponding to a hand rail height, the longitudinally remoteends of the said arms extending at least to each end of said stairs, theupper ends of said arms extending beyond the topmost stair and having arelieved portion at the lower extended edge thereof constructed toengage an upper surface of a landing with the lower ends of said armsshaped to engage a surface of a lower landing to thereby have said armsprovide the principal support for said stairs and the remote ends ofsaid arms having 6 an angle with said stairs so as to be substantiallyperpendicular to the ground when said staircase is installed.

4. A staircase in accordance with claim 3 wherein said relieved portionincludes a horizontal surface substantially on a plane with the topmoststair tread, said horizontal surface being adapted to provide thebearing surface for engagement with the upper surface of a landing.

5. A staircase in accordance with claim 3 wherein said relieved portionincludes an angle iron covering the bearing surfaces of said relievedportion, said angle iron being joined to reinforcing rods embedded inthe concrete of said staircase.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Nb. DatedApril 23, 1974 i It is certified that error appears in theabove-identified pateht and that said Letters Patent are herebycorrected as shown below:

Column 1, line 1: "fluid" should be --field-.

Column 4, line 28 (Claim 2) "landing" should be -leading--.

"configures" should Co1umn 4, line 33 (Claim 2) I be --co figured-.

Signed and sealed this 1st day of October 1974.

(SEAL) Attest: a

McCOY MQ GI BSON JR. 7 c. MARSHALL DANN Attesting Officer Commissionerof Patents USCOMM-DC 003764 59 fir U45. GOVERNMENT PRINTING OFFICE I9890-366-33,

FORM PO-IOSO (IO-69)

1. A mobile unitary precast reinforced concrete staircase and handrailof relatively low weight adapted to span a space between horizontallyand vertically spaced landings comprising a plurality of U-shapedreinforcing rods spaced in generally parallel relationship to oneanother with the arms and base portions of each of said U-shaped rodsbeing in a plane with the corresponding arms and base portions of thebalance of said Ushaped rods longitudinal reinforcing rods extendinggenerally transverse to said U-shaped rods said longitudinal rods beingin spaced and generally parallel relationship to one another with aplurality of longitudinal rods on each arm and on the base portion ofsaid U-shaped rods and weldEd to said U-shaped rods joining them to forma cage, concrete encapsulating said cage to form a U-shaped beam memberwith the concrete of the base of said U-shaped beam member forming aplane on the lower side thereof and being configured on the upperinterior facing side thereof into a plurality of riser and treadsurfaces thereby defining a stairs, each of the arm portions of saidU-shaped beam extending upwardly from said stairs being relatively thinin thickness and integral with said base portion and having the overallshape of a parallelogram with the longitudinal sides thereof parallel tothe general plane of the stairs, said arm portions having a height abovesaid tread surfaces corresponding to a hand rail height, thelongitudinally remote ends of said arm portions extending at least toeach end of said stairs and having an angle therewith so as to besubstantially perpendicular to the ground when said staircase isinstalled.
 2. In combination first and second horizontally andvertically spaced landings, the upper of said landings including a steelplate fastened thereto adjacent the landing edge thereof, a unitaryprecast reinforced concrete staircase of relatively low weight spanningthe space between said landings, said staircase comprised of a unitaryelongated U-shaped beam member of reinforced concrete, the base portionof said U-shaped beam being configures on the upper interior facing sidethereof into a plurality of risers and tread surfaces thereby defining astairs, each of the arm portions of said U-shaped beam being relativelythin in thickness and integral with said base portion and having anoverall shape of a parallelogram with the longitudinal sides thereofparallel to the general plane of the stairs, said arms having a heightgenerally corresponding to a hand rail height, the longitudinally remoteends of said arms extending at least to each end of said stairs with theupper ends of said arms extending beyond said stairs, the ends of saidarms having an angle with said stairs so as to be substantiallyperpendicular to the ground when said staircase is in the installedposition, the portion of said arms extending beyond the upper end ofsaid stairs having a relieved portion at the lower extended edge thereofconstructed and arranged to engage an upper surface of the landing, therelieved portion including an angle iron covering the bearing surfacesof said relieved portion, said angle iron being joined to reinforcingrods embedded in the concrete of said staircase, said angle iron alsobeing joined to said steel plate on said upper landing to preventmovement thereof with respect to said landing and the lower portion ofsaid staircase being in sliding engagement with the upper surface of thelower landing.
 3. A mobile unitary precast reinforced concrete staircaseand handrail of relatively low weight adapted to span a space betweenhorizontally and vertically spaced landings comprising: an elongatedU-shaped beam member comprised of a unitary body of reinforced concrete;the base portion of the said U-shaped beam having a plane surface on theouter side thereof and being configured on the upper interior facingside thereof into a plurality of risers and tread surfaces therebydefining a stairs; each of the arm portions of said U-shaped beam beingrelatively thin in thickness and integral with said base portion andhaving the overall shape of a parallelogram with the longitudinal sidesthereof parallel to the general plane of the stairs, said arms having aheight generally corresponding to a hand rail height, the longitudinallyremote ends of the said arms extending at least to each end of saidstairs, the upper ends of said arms extending beyond the topmost stairand having a relieved portion at the lower extended edge thereofconstructed to engage an upper surface of a landing with the lower endsof said arms shaped to engage a surface of a lower landing to therebyhave said arms provide the principal support for said stairs and tHeremote ends of said arms having an angle with said stairs so as to besubstantially perpendicular to the ground when said staircase isinstalled.
 4. A staircase in accordance with claim 3 wherein saidrelieved portion includes a horizontal surface substantially on a planewith the topmost stair tread, said horizontal surface being adapted toprovide the bearing surface for engagement with the upper surface of alanding.
 5. A staircase in accordance with claim 3 wherein said relievedportion includes an angle iron covering the bearing surfaces of saidrelieved portion, said angle iron being joined to reinforcing rodsembedded in the concrete of said staircase.